High-efficiency dielectric reflection gratings: design, fabrication, and analysis.

We report on reflection gratings produced entirely of dielectric materials. This gives the opportunity to enhance the laser damage threshold over that occurring in conventional metal gratings used for chirped-pulse-amplification, high-power lasers. The design of the system combines a dielectric mirror and a well-defined corrugated top layer to obtain optimum results. The rules that have to be considered for the design optimization are described. We optimized the parameters of a dielectric grating with a binary structure and theoretically obtained 100% reflectivity for the -1 order in the Littrow mounting for a 45 degrees angle of incidence. Subsequently we fabricated gratings by structuring a low-refractive-index top layer of a multilayer stack with electron-beam lithography. The multilayer system was fabricated by conventional sputtering techniques onto a flat fused-silica substrate. The parameters of the device were measured and controlled by light scatterometer equipment. We measured 97% diffraction efficiency in the -1 order and damage thresholds of 4.4 and 0.18 J/cm(2) with 5-ns and 1-ps laser pulses, respectively, at a wavelength of 532 nm in working conditions.

[Speckle photographic studies--a supplementary method for instrumental occlusive analysis]. / Speckle-fotografische Untersuchungen--eine ergänzende Methode zur instrumentellen Okklusionsanalyse.

A new three-dimensional method--speckle photography--introduced into stomatology. For judgement of occlusive and functional interests we examined 20 young adults (10 male and 10 female) aged from 21 to 25. The clinical results together with speckle-photographic model evaluations yield useful hints about morphological and functional connections in the orofacial system.